(a) Field of the Invention
The present invention relates to a log-likelihood ratio (LLR) calculation method, a transmit signal detection method, and a receiver. In particular, the present invention relates a log likelihood ratio calculation method, a transmit signal detection method, and a receiver in a multiple input multiple output (MIMO) system that uses a spatial multiplexing (SM) method.
(b) Description of the Related Art
Recently, mobile communication systems demand to transmission of data at a high speed in fixed and mobile environments. In order to satisfy this demand, an MIMO system that uses an SM method that is capable of transmitting multiple data layers is attracting attention.
The MIMO system that uses the spatial multiplexing method transmits data layers that represent different information through a multiple transmitting antenna and separates the transmitted data layer at a receiving end. In the related art, the transmitted data layers are separated by using a maximum likelihood bit metric detection method that calculates a maximum likelihood bit metric for every transmitting signal vector having combinations available for detecting the optimal transmitting signal to find a transmitting signal vector having the smallest ML metric.
However, the above ML signal detection method has optimal transmitting signal detection performance, but has very high complexity due to the exponential increase of the constellation size and the number of transmitter antennas.